The zinc-finger protein Zelda is a key activator of the early zygotic genome in Drosophila.
In all animals, the initial events of embryogenesis are controlled by maternal gene products that are deposited into the developing oocyte. At some point after fertilization, control of embryogenesis is transferred to the zygotic genome in a process called the maternal-to-zygotic transition. During this time, many maternal RNAs are degraded and transcription of zygotic RNAs ensues. There is a long-standing question as to which factors regulate these events. The recent findings that microRNAs and Smaug mediate maternal transcript degradation have shed new light on this aspect of the problem. However, the transcription factor(s) that activate the zygotic genome remain elusive. The discovery that many of the early transcribed genes in Drosophila share a cis-regulatory heptamer motif, CAGGTAG and related sequences, collectively referred to as TAGteam sites raised the possibility that a dedicated transcription factor could interact with these sites to activate transcription. Here we report that the zinc-finger protein Zelda (Zld; Zinc-finger early Drosophila activator) binds specifically to these sites and is capable of activating transcription in transient transfection assays. Mutant embryos lacking zld are defective in cellular blastoderm formation, and fail to activate many genes essential for cellularization, sex determination and pattern formation. Global expression profiling confirmed that Zld has an important role in the activation of the early zygotic genome and suggests that Zld may also regulate maternal RNA degradation during the maternal-to-zygotic transition.
Liang
Hsiao-Lan
HL
Department of Biology, New York University, 100 Washington Square East, New York, New York 10003, USA.
Nien
Chung-Yi
CY
Liu
Hsiao-Yun
HY
Metzstein
Mark M
MM
Kirov
Nikolai
N
Rushlow
Christine
C
D000818:Animals; D001756:Blastoderm / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics; D029721:Drosophila Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D049750:Genome, Insect / Q000235:genetics*; D008297:Male; D009687:Nuclear Proteins; D020871:RNA Stability; D023121:RNA, Messenger, Stored / Q000235:genetics / Q000378:metabolism; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016335:Zinc Fingers; D015053:Zygote / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*
D029721:Drosophila Proteins; D009687:Nuclear Proteins; D023121:RNA, Messenger, Stored; D014157:Transcription Factors; C512295:zld protein, Drosophila